The present study aims to discuss the still “hot topic” of composition
effects of schools and classrooms on individual achievement development.
Although there is a long research tradition, the effects of school and class-
room composition on individual achievement development are still con-
troversially debated. For example, there is a recent debate to which extent
composition effects on achievement development are mere statistical arti-
facts, so-called “phantom effects.” Overall, one of the issues in this research
area is that the relevant methodological and content-related concepts and
definitions as well as research designs are highly heterogeneous, which
may explain some of this controversy and even contradictory findings.
The article aims to give an overview of the debate of composition effects
on individual achievement development, focusing on especially what this
means for tracked school systems such as the German one. Furthermore, we
discuss both central content-related and methodological questions which
we think should be studied further in theoretical and empirical research.